1. Field of the Invention
This invention relates to specific improvements to a belt grill or belt cooking device and, in particular, to such device useful in fast food type applications wherein large quantities of food portions are cooked rapidly and uniformly.
2. Description of the Prior Art
Belt cooking devices known as belt grills have been in use for processing food products such as hamburgers and other meat patties, chicken and fish filets, pancakes, sandwiches, and other foods. Cooking is achieved by heat conduction to the food product as it is conveyed through heated platens. Typically, a belt grill uses upper and lower platens arranged in parallel planes which are heated by conventional means such as electricity, gas or the like. Opposed belts of flexible, heat resistant material convey the food between the hot platens and in contact therewith so that the uncooked food is fed onto the belt at one end and the cooked product exits the device at the other. The prior art includes both single belt devices and opposed belts. Typically, a belt may be constructed of metal such as stainless steel, links or mesh, or a more flexible material such as Teflon laminated over fiberglass fabric. A typical belt grill is described in U.S. Pat. No. 3,646,880.
In U.S. Pat. No. 5,044,264, a pair of opposed belts are used to convey food products between heated platens, and in that patent grill stripes or marks are transferred onto the food products to simulate cooking on an open grill. The belts are described therein as flexible, heat resistant, typically Teflon laminated over fiberglass fabric so that the cooked product will not tend to stick to the belts.
In U.S. Pat. No. 3,965,807, however, a single conveyor is used with an open design wherein pushers are provided for patties. Patties are then pushed over a lower platen in contact therewith and under an upper platen also in contact for heat by conduction. Obviously, direct contact between the platen and the food to be cooked will require cleaning the platen itself and, presumably, a cool down period to achieve the cleaning periodically. In addition, by using a bar-type open conveyor belt, the food to be cooked must be firm or it will tend to break up. The pressure applied by the platens onto the food also is critical to maintain conductive contact as the food cooks and shrinks. Therefore, this type of apparatus requires more or less skilled operation and maintenance.
Similarly, in U.S. Pat. No. 3,739,711, an open mesh or bar-type single conveyor is used and direct contact is maintained between the platens and the food to be cooked. This device, however, disposes the platens at an angle to the horizontal to facilitate grease removal but it requires that the food to be cooked becomes partially imbedded in the open mesh of the conveyor belt. This also will require cleaning the platens and the mesh belt to remove baked on food particles and the like.
In U.S. Pat. No. 4,567,819, there is described a conveyor-type grill apparatus using upper and lower cooking platens and an endless conveyor wherein the patties are conveyed between the platens into the device, and then returned to be discharged at the front or inlet side of the device. In this way, the size of the unit is diminished but continuous operation becomes difficult. The upper and lower platens also are intended to directly contact the hamburger patties to be cooked but are coated with Teflon to inhibit sticking. This conveyor, however, does dispose the platens at an angle to the horizontal whereby grease removal will be facilitated.
In U.S. Pat. No. 4,667,589 a conveyor grill is described wherein patties are initially cooked on an underside as they pass on an upper conveyor and are then flipped onto a lower conveyor wherein they are cooked on the opposite side. An open mesh conveyor belt is provided and on the second flight of the conveyor, the patties are sandwiched between belts to flatten them. This device does require two flights and, therefore, is a complicated mechanism.
In all such conveyor-type belt grills it is necessary to engage the food product with pressure either between the belts or between the hot platens or both while being cooked so that cooking occurs by conduction. When the cooking surface is the hot platens, however, the lack of flexibility renders the spacing complicated as the food product shrinks.
When the grill is formed with two opposed belts as in U.S. Pat. No. 5,044,264, the food product may be slightly compressed between the upper and lower belts which are flexible as it advances. The belts then can form a nip to receive the food if they are flexible to maintain the desired pressure even though the heated platens above and below the belts are maintained in parallel relationship to each other. When the belts are constructed of a material such as Teflon and they maintain contact with the platen, heat generated by the platens is conducted through the belts and into the item being cooked without the item making direct contact with the platen and while keeping the platens disposed in a parallel relationship to each other. Prior art devices which utilize opposed belts of Teflon rather than open mesh metal have experienced difficulty in adjusting the pressure to be maintained on the food product or in adjusting for different thicknesses of food product to be cooked. In addition, the belts being of a solid material, grease removal in a fast food type operation is a problem. In the less flexible metal-type belts, the grease automatically drains as it accumulates. In the Teflon-coated or other type solid belts, grease can accumulate on the belt itself unless a drainage is provided.
Accordingly, while the use of opposed, flexible heat conductive belts to convey food to be cooked through the cooking area offers distinct advantages to a single mesh-type belt in such a device, it is still necessary to provide for the grease generated in the cooking process and to clean the belts.
In order to maintain Teflon-coated fabric belts at maximum efficiency, tensioners need to be provided in addition to guides which provide a desired nip. Furthermore, in order to minimize downtime for cleaning and other maintenance in which the belts must be removed, it would be desirable to have tensioners which can be readily released. U.S. Pat. No. 3,474,893 describes a conventional single continuous belt conveyor with spring-loaded tensioners provided on rollers which extend downwardly at substantially a 90.degree. angle to the horizontal conveyor flight. The rollers are intended to be adjustably mounted at opposite longitudinal ends and positioned so that the conveyor extends longitudinally over a conveyor table and completely encircles the table with the tensioners applying force to the lower stretch or flight of the conveyor. In this conveyor rotating to a horizontal position releases a belt for quick removal from the conveyor frame. There is no disclosure herein, however, for application of this technology to belt grills.
Accordingly, there is a need for a belt grill wherein the belt spacing may be adjusted readily and wherein downtime for cleaning may be minimized by providing for rapid release and replacement of the individual belts. It is further desired to have automatic and self-adjusting belt tensioning and automatic positioning and repositioning of the platen clearance space. Existing belt grills used in food processing operations which utilize the typical configuration described in the above-identified patents require considerable mechanical disassembly to replace or exchange belts. Additionally, belt-tensioning devices are complex and difficult to adjust. Although food processing operations permit setup time to position the platen clearance, the food service industry application of this type of device cannot tolerate the setup time required when changing food types with existing devices. Similarly, restrictive time requirements for cleaning as well as constraints imposed by available space and consideration for existing methods of grease disposal that exist in the fast food industry may differ significantly from those encountered in food processing operations.